Adoption by olive baboons (Papio anubis) of newly constructed electricity pylons as sleeping sites in Laikipia, Kenya

Abstract Olive baboons (Papio anubis) use fixed, secure, and naturally occurring sleeping sites such as tall trees and rocky cliffs, as protection from predators and often show a selection preference for particular trees or rocky cliff faces. We documented olive baboons' adoption of recently constructed high‐tension electrical transmission towers (pylons) as a novel type of sleeping site in Laikipia, Kenya. The use of pylons suggests that the greatest potential benefits may include reduced parasite exposure and predation avoidance. Thermoregulation and feeding efficiency are not supported as benefits because pylons increase baboons' exposure to wind and cool nighttime temperatures and the pylons were constructed in locations independent of established feeding sites. These observations advance our understanding of olive baboon sleeping site selection in a changing landscape.

and we discuss the implications of this behavior for understanding natural sleeping site preferences.

| MATERIAL S AND ME THODS
Observations were collected on March 5-6, 2023, at the 255 km 2 Agriculture Development Corporation (ADC) Mutara ranch within Laikipia County, Kenya (Figure 2).Laikipia County is a 9700 km 2 region of semi-arid bushland in central Kenya, with a mean annual temperature of 18.3°C (range: 13.0-25.2°C),and a mean total of 812 mm of precipitation annually (monthly mean range: 23-133 mm) (Fick & Hijmans, 2017).ADC Mutara is in the southern part of the greater Laikipia-Samburu ecosystem, which is a mosaic of grassland, Euclea shrubland, as well as Acacia and riverine woodland (Woodroffe & Frank, 2005).The property is served by two semi-permanent rivers, the Suguroi River and the Mutara River, both with riverine habitat.
Tall A. xanthophloea densely occurs along the Suguroi River (Nash & Whitten, 1989), lying between Mutara River and the pylons' used as sleeping sites.Approximately 3 km from those pylons', tall A. xanthophloea sparsely occurring along the seasonal Segera River have typical baboon sleeping site characteristics (Bidner et al., 2018;Isbell et al., 2021)  On the evening of March 5 between 18:00 and 19:00, we opportunistically encountered baboons roosting on pylons during ongoing large mammal surveys by vehicle.After encountering them, we scanned the troops, counting, and aging individuals.We used a Garmin eTrex 10 Global Positioning System (GPS) to record the locations of the roosting sites.We used Empire Model 218 Binoculars (7 × 35) to enhance counting individual baboons in each troop, and a Canon EOS 1300D camera to take photographs to document observations.We returned to the sleeping sites on the morning of March 6th at 06:30, to confirm presence as an overnight sleeping site, and estimate baboon group sizes.We classified troops as separate groups based on distinctly different movement directions the following day.Independent baboon groups are known sometimes to share sleeping sites (Danish & Palombit, 2014).

| RE SULTS
We recorded three troops using pylons as sleeping sites in two dis- pylons and two troops (N.0.08278°, E. 36.75079°)see (Figure 1; Table 1).We encountered another baboon troop using pylons as a sleeping site 2.5 km away (N.0.0909°, E. 36.77193°).We observed two pylons occupied by baboons, but visibility was minimal given low light, and we could not identify demographics at each pylon.All baboons were still atop all pylons at 06:30 on March 6 when we arrived, confirming that all three baboon troops used the pylons as sleeping sites.Total troop sizes were estimated that morning: group one 80 individuals, group two 60, and group three 50 (Table 1).At the first sleeping site, the first group crossed to Ol Pejeta Conservancy, while the second group foraged inside ADC moving northward (Figure 2).
While at the second sleeping site, baboons were observed foraging along the pylons inside ADC Mutara.

| DISCUSS ION
We report a rare observation of three troops of olive baboons utilizing electrical transmission pylons as sleeping sites in Laikipia County, Kenya.Usually, in this landscape, tall Acacia trees and rocky cliffs are predominantly selected as sleeping sites by baboons (Bidner et al., 2018;Hamilton, 1982;Suire et al., 2020).Typically, tall A. xanthophloea with vines and branches overhanging rivers remain preferred sleeping site (Bidner et al., 2018;Isbell et al., 2021).The ADC Mutara landscape is flat and mostly covered by short Vachellia drepanolobium (Figure 1); however, dense patches of tall A. xanthophloea occur along the Suguroi River (Nash & Whitten, 1989), and sparsely at both Mutara and Segera Rivers where baboons were observed previously using as sleeping sites (LL pers.Obs.).
Thermoregulatory benefits do not appear to explain the use of pylons, since the pylons are engineered to minimize wind drag (Jeddi et al., 2023) and, therefore, are less likely than trees and cliffs to shield baboons at night from wind-induced heat loss.Foraging efficiency does not appear to explain sleeping site preferences either, since the pylons were constructed without regard to foraging areas and the baboons still slept in them.A study of baboon ranging behavior before and after pylons were constructed might shed more light on this.Baboons may be selecting pylons to minimize parasite and predator exposure.The pylons' limited surface area may allow feces to drop to the ground more readily, minimizing exposure to gastrointestinal parasites.Moreover, the very tall height and metal design of the pylons are likely to make them difficult for leopards to climb.Pylons also lack the branching structure and foliage cover of trees that can create ambush opportunities for leopards.If pylons TA B L E 1 Observed baboon groups demographics and the use of high-tension electric pylon as sleeping sites in March 2023 at the ADC Mutara Ranch in Laikipia, Kenya.Baboons are known to crop raid (Strum, 2010).With the pylons traversing natural habitat such as ADC Mutara ranch and extending into small-scale farms, they may encourage baboon crop-raiding behavior, potentially resulting in heightened human-wildlife conflicts in this region.Electrocutions from use of anthropogenic power infrastructure have been documented in five species of primates in Kenya including yellow baboons (Katsis et al., 2018), but the survival risk posed by high-tension electrical pylons as sleeping sites remains unknown.Future research is encouraged to investigate the potential costs of the introduction of the transmission line to humans (via increased crop raiding) and baboons (via electrocution) and to determine if improved safety from predators outweighs the risk of electrocution.

Date
and baboons have been observed utilizing them as sleeping sites (LL pers.Obs.).The newly erected pylons intersect Mutara, Suguroi, and Segera Rivers in an east-west direction.The project, dubbed the Ethiopia-Kenya Transmission Interconnection Line, was commissioned in 2006 and launched in 2016 to export up to 2000 MW of electricity (EEPCO & KETRACO, 2012; Tadesse, 2022).The electric pylons are 45 m high, with a square base pillar spread of 17 m and cross arms extending to 15 m (EEPCO & KETRACO, 2012).These arms provide areas where baboons can rest and sleep.
tinct locations.The first sleeping site consisted of three different F I G U R E 1 Three troops of olive baboons (Papio anubis) were observed on March 5, 2023, using recently installed high-tension electric pylons as sleeping sites within Acacia woodland-savannah in Laikipia County, Kenya.
size resting on the ground indeed afford baboons greater protection from parasites or predators, we predict that baboons elsewhere along the transmission line will also adopt pylons as sleeping sites.